Basic Chemistry Concepts: States, Mixtures, and Atomic Structure

Understanding States of Matter

Properties of Solids, Liquids, and Gases

• All are states of matter and are composed of particles.

Solids vs. Liquids

• In solids, particles are very close together and vibrate in fixed positions. Solids have a definite shape and definite volume.
• In liquids, particles are close together but can move past each other. Liquids do not have a definite shape but have a definite volume, taking the shape of their container.

Liquids and Gases

• Both liquids and gases do not have a definite shape; they take the shape of their container.
• Liquids and gases can flow because their molecules are moving and can slide over each other.

Gases

• In gases, particles are far apart and move randomly and rapidly.
• Common examples of gases include oxygen, argon, carbon dioxide, and nitrogen.

Atmospheric Pressure Explained

Atmospheric pressure is the force exerted by the atmosphere on the Earth's surface and all bodies on it, due to the weight of the air above.

Phase Changes: Transformations of Matter

Key Phase Transitions

• Melting: Solid to Liquid
• Boiling: Liquid to Gas (occurs throughout the liquid, with visible bubbles)
• Freezing: Liquid to Solid
• Condensation: Gas to Liquid

Both boiling and evaporation transform liquid to gas, but boiling involves visible bubbling throughout the liquid, while evaporation occurs only at the surface.

Gas Laws: Relationships Between Variables

The behavior of gases is described by relationships between temperature (T), volume (V), and pressure (P).

Understanding Mixtures: Homogeneous vs. Heterogeneous

Heterogeneous Mixtures

Characteristics of heterogeneous mixtures:

• The mixture does not have a uniform composition.
• Each substance forming the mixture retains its individual properties.
• Substances in the mixture can be separated by physical methods.
• Simple methods like sieving or filtration can be used to separate components.

Homogeneous Systems

Characteristics of homogeneous systems:

• Have a uniform distribution and the same physical and chemical properties at all points.
• Homogeneous systems can be:
  • Mixtures: Composed of two or more components (e.g., solutions, colloids).
  • Pure Substances: Single components (e.g., elements, compounds).

Solutions

A solution is a uniform and homogeneous mixture made up of various pure substances in variable proportions.

Colloids

Colloids are mixtures where the particles of the solute cannot be seen by the naked eye, only using a microscope. They are not considered true solutions due to particle size.

Types of Solutions by State of Aggregation

• Liquid Solutions:
  • Water + Solid solute (e.g., salt water)
  • Water + Liquid solute (e.g., alcohol in water)
  • Water + Gaseous solute (e.g., carbonated water)
• Solid Solutions (Alloys):
  • Examples: Steel, Bronze
• Gaseous Solutions:
  • Example: Air (mixture of nitrogen, oxygen, etc.)

Solution Concentration by Proportion

Solutions can be classified by the proportion of solute:

• Dilute: Small amount of solute relative to solvent.
• Concentrated: Large amount of solute relative to solvent.
• Saturated: Contains the maximum amount of solute that can be dissolved at a given temperature.
• Supersaturated: Contains more solute than a saturated solution at the same temperature, typically unstable.

Atomic Structure and Properties

Atoms: The Building Blocks of Matter

Atoms are made up of protons and neutrons located in a central nucleus. Electrons are in constant motion in the space around the nucleus.

Key Atomic Properties

• Atomic Number (Z): The number of protons in an atom. This uniquely identifies an element.
• Mass Number (A): The sum of protons and neutrons in an atom's nucleus.
• Valence: The combining capacity of an atom, representing the exact number of electrons an atom gains, loses, or shares when combining with another atom.